Sequential memory operation without deactivating access line signals

ABSTRACT

Some embodiments include apparatuses and methods for activating a signal associated with an access line coupled to different groups of memory cells during a memory operation of a device, and for sensing data lines of the device during different time intervals of the memory operation to determine the value of information stored in the memory cells. Each of the data lines can be coupled to a respective memory cell of each of the groups of memory cells. In at least one of such apparatuses and methods, the signal applied to the access line can remain activated during the memory operation.

BACKGROUND

Memory devices, such as flash memory, are widely used in computers andmany electronic items. A memory device usually has numerous memorycells. Information can be stored in the memory cells in a writeoperation. The stored information can be obtained from the memory cellsin a read operation. The memory device can also have circuitry to accessthe memory cells. In a memory operation, such as a read or writeoperation, signals can be applied to elements in the circuitry formemory operation. In some conventional memory operations, if suchsignals are poorly controlled, undesirable factors, including increasedpower consumption, increased memory operation time, or both, may occur.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of an apparatus in the form of a memorydevice having a memory array, memory cells, access lines, and datalines, according to an embodiment of the invention.

FIG. 2A shows a schematic diagram of a portion of a memory deviceincluding buffer circuits coupled to data lines, according to anembodiment of the invention.

FIG. 2B is a schematic diagram of a portion of the memory device FIG. 2Ashowing groups of memory cells, according to an embodiment of theinvention.

FIG. 2C shows a schematic diagram of the buffer circuits of the memorydevice of FIG. 2A, according to an embodiment of the invention.

FIG. 3A is a timing diagram for the signals of FIG. 2A, FIG. 2B, andFIG. 2C during an example read operation of the memory device, accordingto an embodiment of the invention.

FIG. 3B is a timing diagram for the signals of FIG. 2A, FIG. 2B, andFIG. 2C during another example read operation of the memory device,according to an embodiment of the invention.

FIG. 3C shows an enlarged portion of some of the signals of FIG. 3B,according to an embodiment of the invention.

FIG. 4 shows a side view of a structure of a portion of a memory deviceincluding memory cells arranged in different levels of the device,according to an embodiment of the invention.

FIG. 5 shows a variation of the memory device of FIG. 4, according to anembodiment of the invention.

FIG. 6 is flow diagram for a method of performing a read operation in amemory device, according to an embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 shows a block diagram of an apparatus in the form of a memorydevice 100 having a memory array 101, memory cells 102, access lines150, and data lines 170, according to an embodiment of the invention.Access lines 150 can include word lines of memory device 100 and can beconfigured to carry signals (e.g., word line signals) WL0 through WLm.Data lines 170 can include bit lines of memory device 100 and can beconfigured to can carry signals (e.g., bit line signals) BL0 throughBLn.

Memory device 100 may use access lines 150 to access memory cells 102during memory operations, and use data lines 170 to exchange information(e.g., data) with memory cells 102. A row decoder 108 and a columndecoder 109 decode address signals AO through AX on lines 103 (e.g.,address lines) to determine which memory cells 102 are to be accessed ina memory operation.

Memory device 100 can perform memory operations such as a read operationto obtain information stored in memory cells 102 and a write (e.g.,programming) operation to write (e.g., program) information to memorycells 102. Memory device 100 can also perform an erase operation toclear information from some or all of memory cells 102.

A memory control unit 118 can be configured to control memory operationsof memory device 100 based on control signals on lines 104. Examples ofthe control signals on lines 104 include one or more clock signals andother signals (e.g., a chip enable signal CE#, a write enable signalWE#) to indicate which operation (e.g., read, write, or erase operation)memory device 100 can perform.

Other devices external to memory device 100 (e.g., a memory accessdevice, such as a processor or a memory controller) can control thevalues of the control signals on lines 104. Specific values of acombination of the signals on lines 104 can produce a command (e.g.,read, write, or erase command) that can cause memory device 100 toperform a corresponding memory operation (e.g., read, write, or eraseoperation).

Memory device 100 can include buffer circuitry (e.g., a page buffercircuit) 120 that can include components such as sense amplifiers andlatches (e.g., data latches). Buffer circuitry 120 can be configured todetermine the value of information stored in memory cells 102 (e.g.,during a read operation) and provide the value of the information in theform of signals Dout0 through Doutn to lines 175 (e.g., part of datalines of memory device 100). Buffer circuitry 120 can also use thesignals on lines 175 to determine the value of information to be stored(e.g., programmed) in memory cells 102 (e.g., during a write operation).

Memory device 100 can include an input/output (I/O) circuit 117 toexchange information between memory array 101 and lines (e.g., I/Olines) 105. Column decoder 109 can selectively activate the CSEL0through CSELn signals based on address signals AO through AX on lines103. I/O circuit 117 can respond to signals CSEL0 through CSELn toselect the signals on lines 175 that can represent the informationobtained from or written to memory cells 102.

Signals DQ0 through DQN on lines 105 can represent information obtainedfrom or written in memory cells 102. Lines 105 can include nodes withinmemory device 100 or pins (or solder balls) on a package where memorydevice 100 can reside. Other devices external to memory device 100(e.g., a memory controller or a processor) can communicate with memorydevice 100 through lines 103, 104, and 105.

Each of memory cells 102 can be configured to store informationrepresenting a value of a fraction of a bit, a value of a single bit, ora value of multiple bits such as two, three, four, or another number ofbits. For example, each of memory cells 102 can be configured to storeinformation representing a binary value “0” or “1” of a single bit(single level cell or SLC). The single bit per cell is sometimes calleda single level cell. In another example, each of memory cells 102 can beconfigured to store information representing a value for multiple bits(multi-level cell or MLC), such as one of four possible values “00”,“01”, “10”, and “11” of two bits, one of eight possible values “000”,“001”, “010”, “011”, “100”, “101”, “110”, and “111” of three bits, orone of other values of another number of multiple bits. A cell that hasthe ability to store multiple bits is sometimes called a multi-levelcell (or multi-state cell).

Memory device 100 can receive supply voltages Vcc and Vss, on lines 106and 107, respectively. Supply voltage Vss can operate at a groundpotential (e.g., having a value of approximately zero volts). Supplyvoltage Vcc can include an external voltage supplied to memory device100 from an external power source such as a battery or analternating-current to direct-current (AC-DC) converter circuitry.

Memory device 100 can include a non-volatile memory device, and memorycells 102 can include non-volatile memory cells, such that memory cells102 can retain information stored thereon when power (e.g., Vcc, Vss, orboth) is disconnected from memory device 100. For example, memory device100 can be a flash memory device, such as a NAND flash or a NOR flashmemory device, or another kind of memory device, such as a variableresistance memory device (e.g., a phase change or resistive randomaccess memory (RAM) device).

Memory device 100 can include a memory device where memory cells 102 canbe physically located in multiple levels on the same device, such thatsome of memory cells 102 can be stacked over some other memory cells 102in multiple levels over a substrate (e.g., a semiconductor substrate) ofmemory device 100.

One of ordinary skill in the art may recognize that memory device 100may include other elements, several of which are not shown in FIG. 1 soas not to obscure the embodiments described herein.

Memory device 100 may include memory devices and operate using memoryoperations (e.g., read, write, and erase operations) similar to oridentical to memory devices and operations described below withreference to FIG. 2A through FIG. 6.

FIG. 2A shows a schematic diagram of a portion of a memory device 200including buffer circuits 220, 221, and 222 coupled to data lines 270,271, and 272, according to an embodiment of the invention. Buffercircuits 220, 221, and 222 can be part of buffer circuitry of memorydevice 200 that can correspond to buffer circuitry 120 of FIG. 1. Duringa memory operation (e.g., a read operation), buffer circuits 220, 221,and 222 can operate to determine the value of information stored inmemory cells 210, 211, 212, and 213. Buffer circuits 220, 221, and 222can provide the value of information, in the form of signals Dout0,Dout1, and Dout2, to an I/O circuit (not shown in FIG. 2A) of memorydevice 200. Such an I/O circuit of memory device 200 can be similar toor identical to I/O circuit 117 of FIG. 1.

As shown in FIG. 2A, data lines 270, 271, and 272 can carry signals BL0,BL1, and BL2, respectively. Each of data lines 270, 271, and 272 can bestructured as a conductive line of memory device 200. Memory device 200can include line 299, which can be structured as a conductive line thatcan form part of a source (e.g., a source line) of memory device 200.Line 299 can carry a signal SL (e.g., source line signal). Memory device200 can include access lines 250 a, 251 a, 252 a, and 253 a that cancarry corresponding signals WL0, WL1, WL2, and WL3. Memory device 200can include control gates 250 b, 251 b, 252 b, and 253 b that can bepart of access lines 250 a, 251 a, 252 a, and 253 a, respectively. FIG.2A shows four access lines 250 a, 251 a, 252 a, and 253 a and three datalines 270, 271, and 272 as an example. The number of such access linesand data lines can vary.

Memory device 200 can include a memory array 202 having memory cells210, 211, 212, and 213, and select transistors 261, 262, 263, 264, 265,and 266. Memory cells 210, 211, 212, and 213 can be arranged in memorycell strings, such as memory cell strings 231 through 239.

Each memory cell string in memory device 200 can be coupled to one ofdata lines 270, 271, and 272 through one of select transistors 264, 265,and 266. Each memory cell string in memory device 200 can also becoupled to line 299 through one of select transistors 261, 262, and 263.For example, memory cell string 231 can be coupled to data line 270through transistor 264 (directly over string 231) and to line 299through transistor 261 (directly under string 231). In another example,memory cell string 232 can be coupled to data line 270 throughtransistor 265 (directly over string 232) and to line 299 throughtransistor 262 (directly under string 232). FIG. 2A shows an example ofnine memory cell strings 231 through 239 and four memory cells 210, 211,212, and 213 in each memory cell string. The number of such memory cellstrings and the number of memory cells in each memory cell string canvary.

As shown in FIG. 2A, some memory cells (e.g., 213) of different memorycell strings (e.g., 231 through 239) can share the same control gate(e.g., 253 b). Some other memory cells (e.g., 212) of these memory cellstrings (e.g., 231 through 239) can share another control gate (e.g.,252 b). Each of control gates 250 b, 251 b, 252 b, and 253 b can bestructured as a single conductive plate.

As shown in FIG. 2A, select transistors 261, 262, and 263 can share thesame gate 280 b. Gate 280 b can form part of a select line (e.g., sourceselect line) 280 a of memory device 200. Select transistors 261, 262,and 263 can be controlled (e.g., turned on or turned off) by the samesignal, such as an SGS signal (e.g., source select gate signal) appliedto select line 280 a. During a memory operation, such as a read or writeoperation, select transistors 261, 262, and 263 can be turned on (e.g.,by activating SGS signal) to couple memory cell strings 231 through 239to line 299. Select transistors 261, 262, and 263 can be turned off(e.g., by deactivating the SGS signal) to decouple the memory cellstrings 231 through 239 from line 299.

Select transistors 264, 265, and 266 can include separate gates (e.g.,separate drain select gates) 284 b, 285 b, and 286 b. However, selecttransistors 264 can share the same gate 284 b. Select transistors 265can share the same gate 285 b. Select transistors 266 can share the samegate 286 b. Gates 284 b, 285 b, and 286 b can form part of select lines(e.g., drain select lines) 284 a, 285 a, and 286 a, respectively, ofmemory device 200.

Select transistors 264, 265, and 266 can be controlled (e.g., turned onor turned off) by corresponding signals SGD0, SGD1, SGD2 (e.g., drainselect gate signals) during a memory operation (e.g., a read or writeoperation) in order to selectively couple the memory cell strings ofmemory device 200 to their respective data lines 270, 271, and 272.During a memory operation (e.g., a read or write operation), only one ofthe signals SGD0, SGD1, and SGD2 can be activated at a time (e.g.,sequentially activated).

For example, during a memory operation, signal SGD0 can be activated toturn on transistors 264 and couple memory cell strings 231, 234, and 237to data lines 270, 271, and 272, respectively. Signals SGD1 and SGD2 canbe deactivated (while signal SGD0 is activated) to decouple memory cellstrings 232, 235, 238, 233, 236, and 239 from data lines 270, 271, and272. In this example, buffer circuits 220, 221, 222 can operate todetermine the values of information stored in selected memory cells ofmemory cell strings 231, 234, and 237 (associated with the activatedsignal SGD0).

In another example, during a memory operation, signal SGD1 can beactivated to turn on transistors 265 and couple memory cell strings 232,235, and 238 to data lines 270, 271, and 272, respectively. Signals SGD0and SGD2 can be deactivated (while signal SGD1 is activated) to decouplememory cell strings 231, 234, 237, 233, 236, and 239 from data lines270, 271, and 272. In this example, buffer circuits 220, 221, 222 canoperate to determine the values of information stored in selected memorycells of memory cell strings 232, 235, and 238 (associated with theactivated signal SGD1).

Memory cells 210, 211, 212, and 213 can arranged such that they can bephysically located in multiple levels of memory device 200, such thatmemory cells 210, 211, 212, and 213 in the same memory cell string canbe stacked over each other (stacked memory cells) in multiple levels ofmemory device 200. FIG. 4 and FIG. 5 show example structures of memorydevices having stacked memory cells that can correspond to memory cells210, 211, 212, and 213 of memory device 200.

FIG. 2B is a schematic diagram of a portion of memory device 200 of FIG.2A showing groups of memory cells 210, 211, 212, and 213, according toan embodiment of the invention. As shown in FIG. 2B, memory cells 213can be grouped into groups 213 ₀, groups 213 ₁, and groups 213 ₂. Memorycells 212 can be grouped into groups 212 ₀, groups 212 ₁, and groups 212₂. Memory cells 211 can be grouped into groups 211 ₀, groups 211 ₁, andgroups 211 ₂. Memory cells 210 can be grouped into groups 210 ₀, groups210 ₁, and groups 210 ₂. Each group of memory cells can correspond toone or more pages in a block of memory cells of memory device 200. Forexample, if memory device 200 is configured as an SLC (single levelcell) memory device, then each group (e.g., group 213 ₀) of memory cellscan correspond to one page in a block of memory cells of memory device200. In another, if memory device 200 is configured as an MLC(multi-level cell, such as two or more bits per cell) memory device,then each group (e.g., group 213 ₀) of memory cells can correspond tomultiple (e.g., two or more) pages in a block of memory cells of memorydevice 200. FIG. 2B shows an example of 12 groups of memory cells whereeach group includes three memory cells. The number of groups of memorycells and the number of memory cells in each group can vary. Forexample, memory device 200 can include hundreds or thousands of pages ina block of memory cells.

Each memory cell group can include one memory cell from a differentmemory string. For example, group 213 ₀ of memory cells 213 can includememory cells 213 from memory cell strings 231, 234, and 237 (coupled toselect line 284 a and access line 253 a in FIG. 2A). Group 213 ₁ ofmemory cells 213 can include memory cells 213 from memory cell strings232, 235, and 238 (coupled to select line 285 a and access line 253 a inFIG. 2A). Group 213 ₂ of memory cells 213 can include memory cells 213from memory cell strings 233, 236, and 239 (coupled to select line 286 aand access line 253 a in FIG. 2A).

In another example, group 212 ₀ of memory cells 212 can include memorycells 212 from memory cell strings 231, 234, and 237 (coupled to selectline 284 a and access line 252 a in FIG. 2A). Group 212 ₁ of memorycells 212 can include memory cells 212 from memory cell strings 232,235, and 238 (coupled to select line 285 a and access line 252 a in FIG.2A). Group 212 ₂ of memory cells 212 can include memory cells 212 frommemory cell strings 233, 236, and 239 (coupled to select line 286 a andaccess line 252 a in FIG. 2A).

During a memory operation (e.g., a read operation), only one of theaccess lines (e.g., 252 a) can be selected at a time. The other accesslines (e.g., 250 a, 251 a, and 253 a) can be unselected access lines.Selecting a particular access line can include activating (e.g.,applying) the signal (e.g., WL2) associated with that particular accessline, such that the signal can be at a particular level (e.g., voltagelevel). Only one of the groups of memory cells (e.g., 212 ₀) coupled tothe selected access line (e.g., 252 a) can be a selected group of memorycells during a particular time interval of a memory operation. Selectinga group of memory cells can include activating the signal (e.g., SGD0 inFIG. 2A) associated with a select line (e.g., 284 a) coupled to thatgroup (e.g., 212 ₀) of memory cells. The memory cells (e.g., 212) fromthe selected group (e.g., 212 ₀) can be concurrently sensed by buffercircuits 220, 221, and 220 (FIG. 2A). Based on the sensed information,buffer circuits 220, 221, and 220 can determine the values informationstored in the memory cells of the selected group (e.g., 212 ₀).

The groups of memory cells coupled to the selected access line (e.g.,252 a) can be selected one group after another (e.g., in a sequentialorder). For example, during a memory operation, if access line 252 a isa selected access line, then groups 212 ₀, 212 ₁, and 212 ₂ of memorycells 212 can be selected in sequential order. In this example, group212 ₀ can be selected (e.g., by activating signal SGD0), then group 212₁ can be selected (e.g., by activating signal SGD1), and group 212 ₂ canbe selected (e.g., by activating signal SGD2) after group 212 ₁ isselected. Thus, in this example, buffer circuits 220, 221, and 222 (FIG.2A) can sense data lines 270, 271, and 272 and sequentially obtaininformation (e.g., one group at a time) from groups 212 ₀, 212 ₁, and212 ₂ of memory cells 212.

FIG. 2C shows a schematic diagram of buffer circuits 220, 221, and 222of FIG. 2A, according to an embodiment of the invention. Buffer circuits220, 221, and 222 can include similar or identical elements (e.g.,transistors, sense amplifiers, and latches) and operate in a mannersimilar to or identical to each other. Similar or identical elementsamong buffer circuits 220, 221, and 222 are given the same designationlabels. For simplicity, detailed description of elements and operationof only buffer circuit 220 are described.

As shown in FIG. 2C, buffer circuit 220 can include elements, such astransistors 241, 242, and 243, a sense amplifier 244, and a latch (e.g.,data latch) 245. FIG. 2C shows an example where these elements arearranged in a single unit (e.g., in the same buffer circuit 220). Someof these elements, however, can be arranged in multiple units separatedfrom buffer circuit 220.

Transistors 241, 242, and 243 can respond to signals CTL1, CTL2, andCTL3, respectively, such that transistors 241, 242, and 243 can beturned on or turned off based on the levels (e.g., voltage level) ofrespective signals CTL1, CTL2, and CTL3. Transistors 241 and 242 caninclude n-channel transistors. Transistor 243 can include a p-channeltransistor.

Transistor 241 can operate to couple data line 270 to other elements ofbuffer circuit 220 (including sense amplifier 244) during a read orwrite operation. Transistor 241 can also operate as a buffer transistorduring an erase operation of memory device 200. Transistor 242 canoperate as a load (e.g., load transistor) when it is turned on and canprovide (e.g., can source) a current from node 247 to data line 270through node 246 during sensing of data line 270. Node 247 can beprovided with a voltage, such as Vcc or another voltage having apositive value (e.g., about 1.5V to 2V). Transistor 243 can operate as atransfer gate (e.g., a pass transistor) when it is turned on to allowsense amplifier 244 to sense data line 270.

Sense amplifier 244 of buffer circuit 220 can respond to a signal SEN(e.g., sense amplifier enable signal) to sense data line 270 during aparticular time interval of a memory operation (e.g., a read operation).Sense amplifier 244 can provide sensed information in the form of asignal SDout0 (e.g., sense output signal). Signal SDout0 can havedifferent levels, depending on the level of signal BL0 on data line 270sensed by sense amplifier 244. The level of signal SDout0 can be used todetermine the value of information (e.g., state) stored in a memory cellof a selected group of memory cells (e.g., a memory cell from one ofmemory cell strings 231, 232, and 233) coupled to data line 270.

Latch 245 of buffer 220 can include a storage element (e.g., staticmemory) to latch (e.g., temporary store) the value of information ondata line 270 sensed by sense amplifier 244. The value of informationstored by latch 245 can depend on the level of signal SDout0 received bylatch 245. The value of information stored by latch 245 can be providedto an I/O circuit (not shown) of memory device 200 in the form of signalDout0. The levels of signal Dout0 can correspond to a binary value(e.g., logic “0” or logic “1”). Latch 245 can respond to a signal SET.Memory device 200 can activate signal SET to set latch 245 to itsinitial state (e.g., zero) after each time latch 245 provides signalDout0 to the I/O circuit of memory device 200.

As shown in FIG. 2C, each of buffer circuits 221 and 222 can includetransistors 241, 242, 243, sense amplifier 244, and latch 245 similar toor identical to those of buffer circuit 220.

Each of buffer circuits 221 and 222 can operate in a manner similar tothat of buffer circuit 220. For example, in buffer circuit 221, senseamplifier 244 can operate to sense data line 271 and provide sensedinformation in the form of a signal SDout1. Signal SDout1 can havedifferent levels, depending on the level of signal BL1 on data line 271sensed by sense amplifier 244 of buffer circuit 221. Latch 245 of buffercircuit 221 can provide signal Dout1 having a level based on the levelof signal SDout1. In buffer circuit 222, sense amplifier 244 can operateto sense data line 272 and provide sensed information in the form of asignal SDout2. Signal SDout2 can have different levels, depending on thelevel of signal BL2 on data line 272 sensed by sense amplifier 244 ofbuffer circuit 222. Latch 245 of buffer circuit 222 can provide signalDout2 having a level based on the level of signal SDout2.

Buffer circuits 220, 221, and 222 can operate to sense (e.g.,concurrently sense) respective data lines 270, 271, and 272. Forexample, during a memory operation (e.g., a read operation) of obtaininginformation stored in group 212 ₀ of memory cells 212 (FIG. 2B), senseamplifiers 244 of buffer circuits 220, 221, and 222 can sense (e.g.,concurrently sense) respective data lines 270, 271, and 272 and providecorresponding signals SDout0, SDout1, and SDout2. In this example, thelevel of signal SDout0 can be based on the value of information (e.g.,state) stored in memory cell 212 of memory cell string 231 (one ofmemory cells 212 in group 212 ₀ in FIG. 2B). The level of signal SDout1can be based on the value of information (e.g., state) stored in memorycell 212 of memory cell string 234 (one of memory cells 212 in group 212₀). The level of signal SDout2 can be based on the value of information(e.g., state) stored in memory cell 212 of memory cell string 237 (oneof memory cells 212 in group 212 ₀).

FIG. 3A is a timing diagram for the signals of FIG. 2A, FIG. 2B, andFIG. 2C during an example read operation of memory device 200, accordingto an embodiment of the invention. FIG. 3A shows different times T0through T5 and different time intervals 301, 302, 303, 312, and 323during the example read operation of memory device 200. Time interval301 can occur between times T0 and T1. Time interval 302 can occurbetween times T2 and T3. Time interval 303 can occur between times T4and T5.

In FIG. 3A, time T0 can occur before time T5. Thus, time interval 301can occur before time interval 302. Time interval 302 can occur beforetime interval 303. Time interval 312 can be between time intervals 301and 302. Time interval 323 can be between time intervals 302 and 303.

V0 through V16 in FIG. 3A represent the different levels (e.g., voltagelevels) that can be provided (e.g., applied) to the signals of memorydevice 200 during different time intervals of the example readoperation.

Each of levels V0 through V16 can correspond to a voltage level. Forexample, level V0 can correspond to a voltage level having a groundpotential (having a value of approximately zero volts, such as Vss inFIG. 1). Each of other levels V1 through V16 can correspond to a voltagelevel having a positive value (e.g., a value greater than groundpotential). Some of levels V0 through V16 can have the same value. Forexample, levels V2, V3, V4, and V5 can have the same value (e.g.,corresponding to the same voltage level, e.g., 5V). Levels V9, V10, andV11 can have the same value (e.g., Vcc). Level V1 can have a valuedifferent from the value of level V2. For example level V1 can have avalue (e.g., 1V) less than the value of level V2 (e.g., 5V). In FIG. 3A,the waveforms including levels V0 through V16 are not scaled.

The example read operation associated with FIG. 3A assumes that accessline 252 a (FIG. 2A) is a selected access line in order to accessselected groups of memory cells coupled to (selected) access line 252 aand obtain information stored in the selected groups of memory cells. Inthis example, groups 212 ₀, 212 ₁, and 212 ₂ of memory cells 212 areassumed to be the selected groups of memory cells (coupled to theselected access line 252 a). Thus, in this example, sense amplifiers 244(FIG. 2C) of buffer circuit 220, 221, and 222 can sense (e.g.,concurrently sense) data lines 270, 271, and 272 and providecorresponding signals SDout0, SDout1, and SDout2 (FIG. 2C). Forsimplicity, only the waveform for SDout0 (associated with buffer circuit220) is shown in FIG. 3A.

In the example read operation associated with FIG. 3A, signal WL2associated with access line 252 a (selected access line) can be referredto as the selected signal (as indicted in FIG. 3A). Signal WL0, WL1, andWL3 associated with access line 250 a, 251 a, and 253 a (unselectedaccess lines) can be referred to as unselected signals (as indicted inFIG. 3A).

At time T0 in FIG. 3A, signal WL2 can be activated (e.g., set), suchthat the level of signal WL2 can be changed from level V0 to level V1.Signal WL2 can remain activated (e.g., can remain set) at the same levelV1 between times T0 and T5. Signal WL2 may not be deactivated (e.g., maynot be reset) at any time interval between times T0 and T5. At time T5,signal WL2 can be deactivated, such that the level of signal WL2 can bechanged (e.g., reset) from level V1 to level V0. Thus, a read operationof memory device 200 can include activating (e.g., setting) the signal(e.g., WL2) associated with a selected access line (e.g., 252 a) tocause the signal to have a certain level (e.g., V1) during the readoperation, without changing (e.g., without resetting) the level of thesignal to a different level, such as without changing (e.g., withoutresetting) the level (e.g., V1) of the signal back to the level (e.g.,V0) that the signal has before it is activated.

Signals WL0, WL1, and WL3 can be activated (e.g., set) in a mannersimilar to that of signal WL2. For example, at time T0 in FIG. 3A,signals WL0, WL1, and WL3 can be activated, such that the level ofsignals WL0, WL1, and WL3 can be changed from level V0 to level V2.Signals WL0, WL1, and WL3 can remain activated (e.g., can remain set) atthe same level V2 between times T0 and T5. Signals WL0, WL1, and WL3 maynot be deactivated (e.g., may not be reset) at any time interval betweentimes T0 and T5. At time T5, signals WL0, WL1, and WL3 can bedeactivated, such that the level of signals WL0, WL1, and WL3 can bechanged (e.g., reset) from level V2 to level V0. Thus, a read operationof memory device 200 can include activating (e.g., setting) the signals(e.g., WL0, WL1, and WL3) associated with unselected access lines (e.g.,250 a, 251 a, and 253 a) to cause those signals to have a certain level(e.g., V2) during the read operation, without changing (e.g., withoutresetting) the level of those signals to a different level, such aswithout changing (e.g., without resetting) the level of the signals backto the level (e.g., V0) that those signals have before they areactivated.

Signal SGS can be activated in a manner similar to that of signals WL0,WL1, and WL3. For example, at time T0 in FIG. 3A, signal SGS can beactivated (e.g., set), such that the level of signal SGS can be changedfrom level V0 to level V6. Signal SGS can remain activated at the samelevel V6 between times T0 and T5. Signal SGS may not be deactivated atany time interval between times T0 and T5. At time T5, signal SGS can bedeactivated (e.g., reset), such that the level of signal SGS can bechanged from level V6 to level V0. Between times T0 and T5, in responseto signal SGS being activated, transistors 261, 262, and 263 (FIG. 2A)can turn on to couple memory cell strings 231, 234, and 237 to line 299.Since signal SGS can remain activated between times T0 and T5,transistors 261, 262, and 263 can remain turned on between times T0 andT5. Thus, a read operation of memory device 200 can include activating(e.g., setting) the signal (e.g., SGS) associated with a select line(e.g., 280 a) to cause the signal to have a certain level (e.g., V6)during the read operation, without changing (e.g., without resetting)the level of the signal to a different level, such as without changingthe level of the signal back to the level (e.g., V0) that the signal hasbefore it is activated.

As shown in FIG. 3A, signals SGD0, SGD1, and SGD2 can be activated oneat a time (e.g., sequentially activated) between times T0 and T5, suchthat only one of signals SGD0, SGD1, and SGD2 can be activated during aparticular time interval while the other signals (among signals SGD0,SGD1, and SGD2) can be deactivated. For example, during time interval301, signal SGD0 can be activated to level V3 while signals SGD1 andSGD2 can be deactivated (e.g., remain at level V0). During time interval302, signal SGD1 can be activated to level V4 while signals SGD0 andSGD2 can be deactivated (e.g., remain at level V0). During time interval303, signal SGD2 can be activated to level V5 while signals SGD0 andSGD1 can be deactivated (e.g., remain at level V0).

During time interval 301 (e.g., sense time interval), in response tosignal SGD0 being activated, transistors 264 (FIG. 2A) can turn on tocouple memory cell strings 231, 234, and 237 to data lines 270, 271, and272, respectively. Sense amplifiers 244 (FIG. 2C) can sense data lines270, 271, and 272 and provide sensed information to latches 245. Latches245 (FIG. 2C) can latch the sensed information and provide it to an I/Ocircuit of memory device 200. The sensed information during timeinterval 301 can be based on the values of information stored in group212 ₀ of memory cells 212 (FIG. 2B), which are memory cells 212 frommemory cell strings 231, 234, and 237 coupled to data lines 270, 271,and 272, respectively, during time interval 301.

During time interval 302 (e.g., sense time interval), in response tosignal SGD1 being activated, transistors 265 (FIG. 2A) can turn on tocouple memory cell strings 232, 235, and 238 to data lines 270, 271, and272, respectively. Sense amplifiers 244 (FIG. 2C) can sense data lines270, 271, and 272 and provide the sensed information to latches 245.Latches 245 can latch the sensed information and provide it to an I/Ocircuit of memory device 200. The sensed information during timeinterval 302 can be based on the values of information stored in group212 ₁ of memory cells 212 (FIG. 2B), which are memory cells 212 frommemory cell strings 232, 235, and 238 coupled to data lines 270, 271,and 272, respectively, during time interval 302.

During time interval 303 (e.g., sense time interval), in response tosignal SGD2 being activated, transistors 266 (FIG. 2A) can turn on tocouple memory cell strings 233, 236, and 239 to data lines 270, 271, and272, respectively. Sense amplifiers 244 (FIG. 2C) can sense data lines270, 271, and 272 and provide the sensed information to latches 245.Latches 245 can latch the sensed information and provide it to an I/Ocircuit of memory device 200. The sensed information during timeinterval 303 can be based on the values of information stored in group212 ₂ of memory cells 212 (FIG. 2B), which are memory cells 212 frommemory cell strings 233, 236, and 239 coupled to data lines 270, 271,and 272, respectively, during time interval 303.

The value of the sensed information can correspond to the levels ofsignals BL0, BL1, and BL2 (FIG. 2A and FIG. 2C). For simplicity, onlythe waveform of signal BL0 associated with data line 270 is shown inFIG. 3A.

Signal BL0 can have level V7 or level V8 during each of time intervals301, 302, and 303 (e.g., sense time intervals). Level V7 can have apositive value, such as a positive voltage value (e.g., Vcc). Level V8can have a positive value, such as a positive voltage value (e.g., avoltage value greater than ground potential and less than 0.5V).

During each of time intervals 301, 302, and 303, sense amplifier 244(FIG. 2C) of buffer circuit 220 can sense data line 270 and providesensed information. The level (e.g., V7 or V8) of signal BL0 during aparticular time interval (e.g., one of time intervals 301, 302, and 303)can be based on the value of information stored in memory cell 212 ofone of memory cell strings 231, 232, and 233 (FIG. 2A) that is coupledto data line 270 during that particular time interval.

For example, during time interval 301, memory cell 212 of memory cellstring 231 can be coupled to data line 270 (because signal SDG0 isactivated during time interval 301). Thus, during time interval 301, thelevel of signal BL0 can be based on the value of information stored inmemory cell 212 of memory cell strings 231. For example, signal BL0 canhave level V7 if the information stored in memory cell 212 of memorycell string 231 has one value (e.g., logic “0”). Signal BL0 can havelevel V8 if the information stored in memory cell 212 of memory cellstring 231 has another value (e.g., logic “1”).

During time interval 302, memory cell 212 of memory cell string 232 canbe coupled to data line 270 (because signal SDG1 is activated duringtime interval 302). Thus, during time interval 302, the level of signalBL0 can be based on the value of information stored in memory cell 212of memory cell string 232.

During time interval 303, memory cell 212 of memory cell string 233 canbe coupled to data line 270 (because signal SDG2 is activated duringtime interval 303). Thus, during time interval 303, the level of signalBL0 can be based on the value of information stored in memory cell 212of memory cell string 233.

Signal SDout0 can have a level corresponding to sensed informationsensed by sense amplifier 244 of buffer circuit 220 during timeintervals 301, 302, and 303. Signal SDout0 can have levels based on thelevels of signal BL0. For example, signal SDout0 can have level V15 ifsignal BL0 has level V8 and level V16 if signal BL0 has level V7. Duringtime interval 301, the level of signal SDout0 can be used to determinethe value of information stored in memory cell 212 of memory cell string231. For example, during time interval 301, if signal SDout0 has levelV15, then the value of information stored in memory cell 212 of memorycell string 231 can be determined to be at one value (e.g., logic “0”).If signal SDout0 has level V16, then the value of information stored inmemory cell can be determined to be at another value (e.g., logic “1”).The level of signal SDout0 during time interval 302 can be used todetermine the value of information stored in memory cell 212 of memorycell string 232. The level of signal SDout0 during time interval 303 canbe used to determine the value of information stored in memory cell 212of memory cell string 233.

As shown in FIG. 3A, signal CTL1 can be provided with level V9 betweentimes T0 and T5 to turn on transistors 241 (FIG. 2C) during a timeinterval between times T0 and T5. Signal CTL2 can be provided with levelV0 during time intervals 301, 302, and 303 to turn on transistor 242during time intervals 301, 302, and 303. Data line 270 is coupled tonode 247 when transistor 242 is turned on. Signal CTL2 can be providedwith level V10 during time intervals 312 and 323 to turn off transistor242 during time intervals 312 and 323. Data line 270 is decoupled fromnode 247 when transistor 242 is turned off. Signal CTL3 can be providedwith level V11 during time intervals 301, 302, and 303 to turn ontransistor 243 during time intervals 301, 302, and 303. Signal CTL3 canbe provided with level V0 during time intervals 312 and 323 to turn offtransistor 243 during time intervals 312 and 323.

Signal SET can be provided with level V13 during time intervals 312 and323 to set latches 245 of buffer circuits 220, 221, and 222 (FIG. 2C) toa state (e.g., an initial state, such as zero). For example, during eachof time intervals 301, 302, and 303, sense amplifiers 244 can perform asensing stage to sense data lines 270, 271, and 272. Latches 245 can beset to an initial state during a time interval between two sensingstages. For example, latches 245 can be set to an initial state duringtime interval 312, which is between a sensing stage performed duringtime interval 301 and another sensing stage performed during timeinterval 302. In another example, latches 245 can be set to an initialstate during time interval 323, which is a time interval between asensing stage performed during time interval 302 and another sensingstage performed during time interval 303.

Memory device 200 may perform a memory operation of obtaininginformation stored in memory cells 210, 211, 212, and 213 withoutcharging (e.g., without precharging) data lines 270, 271, and 272between two sensing stages. For example, during each of time intervals312 and 323, memory device 200 may not precharge data lines 270, 271,and 272 by, for example, not coupling data lines 270, 271, and 272 to avoltage source (e.g., to Vcc or to another positive voltage).

In the above description with reference to FIG. 2A, FIG. 2B, FIG. 2C,and FIG. 3A, groups 212 ₀, groups 212 ₁, and groups 212 ₂ of memorycells 212 (FIG. 2B) coupled to access line 252 a (associated with signalWL2) are selected to be accessed to obtain information from them duringa read operation, as an example. Other groups of memory cells coupled tothe same access line can also be selected and accessed in a mannersimilar to that used for groups 212 ₀, groups 212 ₁, and groups 212 ₂ ofmemory cells 212 during the example read operation described above. Forexample, if groups 210 ₀, groups 210 ₁, and groups 210 ₂ of memory cells210 (FIG. 2B) coupled to access line 250 a (associated with signal WL0)are selected to be accessed to obtain information from them during aread operation, then access line 250 a and signal WL0 can be theselected access line and the selected signal, respectively; the otheraccess lines 251 a, 252 a, and 253 a can be unselected access lines. Inthis case, activities and operations to obtain information stored ingroups 210 ₀, groups 210 ₁, and groups 210 ₂ of memory cells 210 can besimilar to those described above with reference to reference to FIG. 2A,FIG. 2B, FIG. 2C, and FIG. 3A for groups 212 ₀, groups 212 ₁, and groups212 ₂ of memory cells 212.

FIG. 3B is a timing diagram for the signals of FIG. 2A, FIG. 2B, andFIG. 2C during another example read operation of memory device 200,according to an embodiment of the invention. The timing diagram in FIG.3A (described above) may be associated with memory device 200 when eachof the memory cells (e.g., 210, 211, 212, and 213) of memory device 200is configured as a single level cell. The timing diagram in FIG. 3B(described below) may be associated with memory device 200 when each ofthe memory cells (e.g., 210, 211, 212, and 213) of memory device 200 isconfigured as a multi-level cell (e.g., 2-bit per cell, for the exampleassociated with FIG. 3B)

The differences between FIG. 3A and FIG. 3B include differences in thewaveforms for signals WL2, signal CTL3, and signal SEN. FIG. 3C shows anenlarged portion of signals WL2, CTL3, and SEN of FIG. 3B. The waveformsfor other signals (signals besides signals WL2, CTL3, and SEN) in FIG.3B can be activated and deactivated in a manner similar to or identicalto that described above with reference to FIG. 3A. Thus, for simplicity,the descriptions for the other signals for are not repeated in thedescription with reference to FIG. 3B.

As shown in FIG. 3B, signal WL2 can be activated (e.g., set) at time T0from level V0 and can remain activated at level V1 ₀, V1 ₁, or V1 ₂between times T0 and T5. Signal WL2 may not be deactivated (e.g., maynot be reset back to level V0) at any time interval between times T0 andT5. FIG. 3B shows an example where signal WL2 can be provided with threedifferent levels (V1 ₀, V1 ₁, and V1 ₂) during each of time intervals301, 302, and 303 to indicate that each of memory cells 210, 211, 212,and 213 (FIG. 2A) of memory device 200 may be configured as a 2-bit percell (e.g., each memory cell can store two bits). The number ofdifferent levels of signal WL2 during each of time intervals 301, 302,and 303 can vary. For example, if each of memory cells 210, 211, 212,and 213 of memory device 200 is configured as a 3-bit per cell (e.g.,each memory cell can store three bits), then signal WL2 in FIG. 3B canbe provided with seven different levels (e.g., V1 ₀ through V1 ₆).

As mentioned above, in the example associated with FIG. 3B, each ofmemory cells 210, 211, 212, and 213 of memory device 200 is configuredas a 2-bit per cell. Thus, each of memory cells 210, 211, 212, and 213can store one of four possible values of two bits, such as “00”, “01”,“10”, or “11”. In this example, memory device 200 can be configured toinclude four different threshold voltage (Vth) ranges (e.g., Vthdistributions) associated with cells 210, 211, 212, and 213. The voltagevalue in each of the four Vth ranges can be used to represent one offour possible values of information stored in each memory cell. Forexample, memory device 200 can be configured to include four Vth rangesincluding Vth₀ range, Vth₁ range, Vth₂ range, and Vth₃ range torepresent values “11”, “10”, “00”, and “01”, respectively, of two bits.Vth₀ range, Vth₁ range, Vth₂ range, and Vth₃ range can be arranged froma lower Vth range to a higher Vth range. For example, among these Vthranges, Vth₀ range can be lowest Vth range (e.g., a lowest voltage valuerange) and Vth₃ range can be a highest Vth range (e.g., a highestvoltage value range). Thus, values “11”, “10”, “00”, and “01”, in thisorder, can go from a lowest threshold voltage value to a highestthreshold voltage value, with “11” corresponding to the lowest thresholdvoltage value. The order “11”, “10”, “00”, and “01” is used as anexample. Other orders can be used.

The different levels of signal WL2 during each of time intervals 301,302, and 303 in FIG. 3B allows memory device 200 to determine the valueof information stored in selected memory cells during a read operationin the example associated with FIG. 3B. The selected memory cells theexample associated with FIG. 3B can be similar to those of the selectedmemory cells in the example associated with FIG. 3A. For example, theselected memory cells during time interval 301 in FIG. 3B can includememory cells 212 in group 212 ₀ (FIG. 2B). The selected memory cellsduring time interval 302 in FIG. 3B can include memory cells 212 ingroup 212 ₁ (FIG. 2B). The selected memory cells during time interval303 in FIG. 3B can include memory cells 212 in group 212 ₂ (FIG. 2B).

During each of time intervals 301, 302, and 303 in FIG. 3B, levels V1 ₀,V1 ₁, and V1 ₂ of signal WL2 can be used to determine the value ofinformation stored in memory cells that are selected to obtaininformation stored in them. For example, level V1 ₀ of signal WL2 can beused to determine (e.g., judge) whether the Vth of a selected cell(which is selected to obtain information store in it) is less than Vth₁range or at least equal to (equal to or greater than) a value in Vth₁range. If the Vth of a selected cell is less than Vth₁ range, then thevalue of information stored in the selected memory cell can bedetermined to be corresponding to Vth₀ range (e.g., value “11”). If theVth of a selected cell is at least equal to Vth₁ range, then level V1 ₁,level V1 ₂, or both (as described below) of signal WL2 can be used todetermine the value of information (e.g., “00” or “01”) stored in theselected memory cell.

Level V1 ₁ of signal WL2 in FIG. 3B can be used to determine whether theVth of a selected cell is less than Vth₂ range or at least equal to avalue in Vth₂ range. If the Vth of a selected cell is less than Vth₂range, then the value of information stored in the selected memory cellcan be determined to be corresponding to Vth₁ range (e.g., value “10”).If the Vth of a selected cell is at least equal to Vth₂ range, thenlevel V1 ₂ of signal WL2 can be used to determine the value ofinformation stored in the selected memory cell (e.g., “00” or “01”)

Level V1 ₂ of signal WL2 in FIG. 3B can be used to determine whether theVth of a selected cell is less than Vth₃ range or at least equal to avalue in Vth₃ range. If the Vth of a selected cell is less than Vth₃range, then the value of information stored in the selected memory cellcan be determined to be corresponding to Vth₂ range (e.g., value “00”).If the Vth of a selected cell is at least equal to Vth₃ range, then thevalue of information stored in the selected memory cell can bedetermined to be corresponding to Vth₃ range (e.g., value “01”).

As shown in FIG. 3C, during each of levels V1 ₀, V1 ₁, and V1 ₂ ofsignal WL2, signal CTL3 can be activated from level V0 to level V11 andsignal CTL3 can be activated from level V0 to level V12. Senseamplifiers 244 (FIG. 2C) can sense data lines 270, 271, and 272 eachtime signal SEN is activated and provide sensed information to latches245. Latches 245 (FIG. 2C) can latch the sensed information and provideit to the I/O circuit of memory device 200.

Providing a memory device, such as memory device 200, and operating thememory device during a memory operation (e.g., a read operation), asdescribed above with reference to FIG. 1 through FIG. 3B, may improvepower consumption of the memory device during the memory operation. Thememory operation time used to obtain information stored in the memorycells of the memory device may also be improved. For example, sincesignals WL0, WL1, WL2, and WL3 (FIG. 3A) can remain activated (e.g.,without resetting it to V0) during a memory operation (e.g., a readoperation), one or both of power consumption and memory operation timemay be reduced. Further, since data lines (e.g., 270, 271, and 272) ofmemory device 200 can be sensed to obtain information stored indifferent groups of memory cells without precharging the data linesbetween sensing stages, one or both of power consumption and memoryoperation time may also be improved (e.g., reduced).

FIG. 4 shows a side view of a structure of a portion of a memory device400, according to an embodiment of the invention. Memory device 400 caninclude a memory device described above with reference to FIG. 1 throughFIG. 3C, such as memory device 200 (FIG. 2A). Thus, similar or identicalelements (e.g., memory cells, data lines, control gates) between memorydevice 200 and memory device 400 are given the same designation labels.

As shown in FIG. 4, memory device 400 can include a substrate 490 wherememory cell string 231 can be formed over substrate 490. FIG. 4 showsonly one memory cell string 231. Other memory cell strings of memorydevice 400 can be formed over substrate 490 and can have a structuresimilar to or identical to that of memory cell string 231. Substrate 490can include a monocrystalline (also referred to as single-crystal)semiconductor material (e.g., single-crystal silicon). Themonocrystalline semiconductor material of substrate 490 can includeimpurities, such that substrate 490 can have a specific conductivitytype (e.g., n-type or p-type).

As shown in FIG. 4, memory cells 210, 211, 212, and 213 can be locatedin different levels 421, 422, 423, and 424, respectively, in az-direction of memory device 200. The z-direction can extend in adirection (e.g., vertical direction) associated with the thickness ofsubstrate 490. FIG. 4 also shows an x-direction, which can extend in adirection (e.g., horizontal) perpendicular to the z-direction.

Memory cell string 231 can include a body 440 having a portion 441coupled to data line 270 and a portion 442 coupled to line 299. Body 440can include a conductive material that is capable of providing aconduction of current between data lines 270 and 299. Portions 441 and442 can include materials of different conductivity types. For example,portion 441 can include a semiconductor material of n-type, and portion442 can include a semiconductor material of p-type. The semiconductormaterial can include polycrystalline silicon.

Control gates 250 b, 251 b, 252 b, and 253 b can be located along atleast a portion (e.g., portion 442) of body 440 in the z-direction. Thematerials of control gates 250 b, 251 b, 252 b, and 253 b can include aconductive material (e.g., conductively doped polycrystalline silicon orother conductive material).

Memory cell string 231 can include materials 403, 404, 405 between aportion of body 440 and each of control gates 250 b, 251 b, 252 b, and253 b. Material 405 can also be between body 440 and each of gates 280 band 284 b. As shown in FIG. 4, materials 403, 404, and 405 can beseparated among memory cells 210, 211, 212, and 213.

Material 403 can include a charge blocking material(s) (e.g., adielectric material such as silicon nitride) that is capable of blockinga tunnel of a charge.

Material 404 can include a charge storage material(s) that can provide acharge storage function to represent a value of information stored inmemory cell 210, 211, 212, and 213. For example, material 404 caninclude conductively doped polycrystalline silicon, which can be eithera p-type polycrystalline silicon or an n-type polycrystalline silicon.The polycrystalline silicon can be configured to operate as a floatinggate (e.g., to store charge) in a memory cell (e.g., a memory cell 210,211, 212, or 213).

Material 405 can include a tunnel dielectric material(s) (e.g., an oxideof silicon) that is capable of allowing tunneling of a charge (e.g.,electrons).

Line 299 can be formed over substrate 490. Line 299 and portion 442 ofbody 440 can include materials of different conductivity types. Forexample, line 299 can include a semiconductor (e.g., polycrystallinesilicon) material of n-type, and portion 442 can include a semiconductor(polycrystalline silicon) material of p-type.

Line 299 and portion 441 of body 440 can include materials of the sameconductivity type (e.g., polycrystalline silicon of n-type). As shown inFIG. 4, portions 441 and 442 can contact each other and form a junction(e.g., p-n junction) 443. Portion 442 and line 299 can contact eachother and form a junction (e.g., p-n junction) 444.

FIG. 4 shows line 299 formed over substrate 490 as an example. In analternative arrangement, line 299 can be formed in a portion ofsubstrate 490. For example, line 299 can be a part of substrate 490 thatis doped with impurities to create a conductivity type (e.g., n-type orp-type) different from another part of substrate 490.

Memory device 400 can include buffer circuitry 420 located over (e.g.,formed in or formed on) a portion of substrate 490. Buffer circuitry 420can include buffer circuits, such as buffer circuits 220, 221, and 222of memory device 200 (FIG. 2C). Memory device 400 can include conductivepaths (not shown in FIG. 4) to couple buffer circuitry 420 to otherelements of memory device 400 (e.g., data line 270). Memory device 400can be configured to perform memory operations (e.g., read, write, anderase operation) similar to or identical to those described above withreference to FIG. 1 through FIG. 3C.

FIG. 5 shows a memory device 500, which can be variation of memorydevice 400 of FIG. 4, according to an embodiment of the invention. Asshown in FIG. 5, memory device 500 can include elements that are similarto or identical to those of memory device 400 of FIG. 4. For simplicity,similar or identical elements between memory devices 400 and 500 are notrepeated in the description with reference to FIG. 5. As shown in FIG.5, materials 403, 404, and 405 are not separated (e.g., continuous)among memory cells 210, 211, 212, and 213. Material 404 of FIG. 5 can bedifferent from material 404 of FIG. 4. For example, material 404 of FIG.5 can include charge trapping materials, such as silicon nitride.

FIG. 6 is flow diagram for a method 600 of performing a read operationin a memory device, according to an embodiment of the invention. Method600 can be used in a memory device such as memory device 100 (FIG. 1),memory device 200 (FIG. 2A, FIG. 2B, and FIG. 2C), memory device 400,and memory device 500 (FIG. 5).

As shown in FIG. 6, activity 610 of method 600 can include receiving acommand (e.g., a read command) to perform a memory operation (e.g., aread operation) of obtaining information stored in memory cells of thememory device. The command received in activity 610 can be provided tothe memory device by a memory controller or a processor external to thememory device.

Activity 620 of method 600 can include applying signals to linesincluding access lines of the memory device during the memory operation.The access lines can include access lines 250 a, 251 a, 252 a, and 253 aof memory device 200 of FIG. 2A. The signals applied in activity 620 caninclude signals WL0, WL1, WL2, and WL3 (FIG. 2A).

In activity 620, applying the signals can include activating thesignals, such that the levels of the signals can be changed from onelevel to another level. The signals can remain activated at the samelevel during the memory operation. The waveforms of the signals can besimilar or identical to those of signals WL0, WL1, WL2, and WL3 shown inFIG. 3A. Thus, activity 620 can include activating (e.g., setting) thesignals to cause the signals to have certain levels during the memoryoperation, without changing (e.g., without resetting) the levels of thesignals to different levels, such as without changing the levels of thesignals back to the levels (e.g., V0 in FIG. 3A) that the signals havebefore they are activated.

Activity 630 of method 600 can include obtaining information stored inmemory cells of the memory device. Obtaining the information in activity630 can include sensing data lines coupled to the selected groups ofmemory cells among the memory cells of the device and latching thesensed information. The groups of memory cells in activity can includegroups 212 ₀, 212 ₁, and 212 ₁ of memory cells 212 of FIG. 2C. Thus,obtaining the information in activity 630 can include activities andoperations associated the example read operation described above withreference to FIG. 3A.

Activity 640 of method 600 can include providing the informationobtained from the memory cell to other elements of the memory device,such as to an I/O circuit of the memory device.

Method 600 can include fewer or more activities relative to activities610, 620, 630, and 640 shown in FIG. 6. For example, method 600 mayinclude activities and operations of a read operation described abovewith reference to FIG. 1 through FIG. 3C.

The illustrations of the apparatuses (e.g., memory devices 100, 200,400, and 500) and methods (e.g., method 600 and operations performed bymemory devices 100, 200, 400, and 500) are intended to provide a generalunderstanding of the structure of various embodiments and are notintended to provide a complete description of all the elements andfeatures of an apparatus that might make use of the structures describedherein.

The apparatuses (e.g., memory devices 100 and 200 or part of memorydevices 100 and 200, including memory control unit 118 of FIG. 1, buffercircuitry 120 of FIG. 1, buffer circuits 220, 221, and 222 of FIG. 2Aand FIG. 2C) described above may all be characterized as “modules” (or“module”) herein. Such modules may include hardware circuitry, singleand/or multi-processor circuits, memory circuits, software programmodules and objects and/or firmware, and combinations thereof, asdesired and/or as appropriate for particular implementations of variousembodiments.

Memory device 100, 200, 400, or 500 may be included in apparatuses(e.g., electronic circuitry) such as high-speed computers, communicationand signal processing circuitry, single or multi-processor modules,single or multiple embedded processors, multi-core processors, messageinformation switches, and application-specific modules includingmultilayer, multi-chip modules. Such apparatuses may further be includedas sub-components within a variety of other apparatuses (e.g.,electronic systems), such as televisions, cellular telephones, personalcomputers (e.g., laptop computers, desktop computers, handheldcomputers, tablet computers, etc.), workstations, radios, video players,audio players (e.g., MP3 (Motion Picture Experts Group, Audio Layer 3)players), vehicles, medical devices (e.g., heart monitor, blood pressuremonitor, etc.), set top boxes, and others.

The embodiments described above with reference to FIG. 1 through FIG. 5include apparatuses and methods for activating a signal associated withan access line coupled to different groups of memory cells during amemory operation of a device, and for sensing data lines of the deviceduring different time intervals of the memory operation to determine thevalue of information stored in the memory cells. Each of the data linescan be coupled to a respective memory cell of each of the groups ofmemory cells. In at least one of such apparatuses and methods, thesignal applied to the access line can remain activated during the memoryoperation. Other embodiments including additional apparatuses andmethods are described.

The above description and the drawings illustrate some embodiments ofthe invention to enable those skilled in the art to practice theembodiments of the invention. Other embodiments may incorporatestructural, logical, electrical, process, and other changes. Examplesmerely typify possible variations. Portions and features of someembodiments may be included in, or substituted for, those of others.Many other embodiments will be apparent to those of skill in the artupon reading and understanding the above description.

What is claimed is:
 1. A method comprising: controlling a first selecttransistor and a second select transistor during a memory operation ofobtaining information stored in a memory cell of a first memory cellstring and a second memory cell of a second memory cell string of adevice, such that the first select transistor is turned on during afirst time interval, and such that the second select transistor isturned on during a second time interval, the first select transistorcoupled between a data line and the first memory cell string, the secondselect transistor coupled between the data line and the second memorycell string, each of the first and second memory cell strings includingmemory cells located in different levels of the device; and applying asignal having a level greater than ground potential to an access linecoupled to the first and second memory cell strings during the memoryoperation of obtaining information stored in the first and second memorycell strings without resetting the signal during the memory operation ofobtaining information stored in the first and second memory cellstrings, wherein the data line is not precharged between the first andsecond time intervals.
 2. The method of claim 1, further comprising:applying an additional signal having a level greater than groundpotential to an additional access line coupled to the first and secondmemory cell strings during the memory operation of obtaining informationstored in the first and second memory cell strings without changing thelevel of the additional signal during the memory operation of obtaininginformation stored in the first and second memory cell strings.
 3. Themethod of claim 2, wherein the level of the signal applied to the accessline and the level of the additional signal applied to the additionalaccess line have different values.
 4. The method of claim 1, furthercomprising: sensing the data line when the first select transistor isturned on; and sensing the data line when the second select transistoris turned on.
 5. A method comprising: controlling a first selecttransistor and a second select transistor during a memory operation ofobtaining information stored in a memory cell of a first memory cellstring and a second memory cell of a second memory cell string of adevice such that the first select transistor is turned on during a firsttime interval, and such that the second select transistor is turned onduring a second time interval, the first select transistor coupledbetween a data line and the first memory cell string, the second selecttransistor coupled between the data line and the second memory cellstring, each of the first and second memory cell strings includingmemory cells located in different levels of the device; applying asignal having a level greater than ground potential to an access linecoupled to the first and second memory cell strings during the memoryoperation of obtaining information stored in the first and second memorycell strings without resetting the signal during the memory operation ofobtaining information stored in the first and second memory cellstrings; and controlling a third select transistor and a fourth selecttransistor during the memory operation, such that the third and fourthtransistors remain turned on during the memory operation, the thirdtransistor coupled between a source of the device and the first memorycell string, the fourth select transistor coupled between the source andthe second memory cell string.
 6. The method of claim 5, wherein thesignal applied to the access line has a ground potential before thesignal is activated.
 7. A method comprising: applying a signal to anaccess line during a memory operation of a device, the access linecoupled to a first memory cell string and a second memory cell string,each of the first and second memory cell strings including memory cellslocated in different levels of the device; activating a signalassociated with a first select line during a first time interval of thememory operation, the first select line coupled to a ate of a firstselect transistor the first select transistor coupled between the firstmemory cell string and a data line; activating a signal associated witha second select line during a second time of the memory operation, thesecond select line coupled to a ate of a second select transistor thesecond select transistor coupled between the second memory cell stringand the data line; determining a value of information stored in a memorycell of the first memory string during the first time interval anddetermining a value of information stored in a memory cell of the secondmemory string during the second time interval, wherein the signalapplied to the access line is not reset between the first and secondtime intervals; deactivating the signal associated with the first selectline during the time interval between the first and second timeintervals; and activating a signal associated with a third select lineduring the first and second time intervals, the third select linecoupled to a gate of a third select transistor and a gate of a fourthselect transistor, wherein the signal associated with the third selectline remains activated during the time interval between the first andsecond time intervals.
 8. The method of claim 7, further comprising:coupling the data line to a voltage during the first and second timeintervals, the voltage having a positive value; and decoupling the dataline from the voltage during the time interval between the first andsecond time intervals.
 9. The method of claim 8, further comprising:applying an additional signal to an additional access line during thememory operation, the additional access line coupled to the first andsecond memory cell strings, wherein the additional signal has a samelevel during the first and second time intervals and during the timeinterval between the first and second time intervals.
 10. An apparatuscomprising: an access line; a data line; a first memory cell stringcoupled to the access line and the data line, the first memory cellstring including memory cells located in different levels of theapparatus; a second memory cell string coupled to the access line andthe data line, the second memory cell string including memory cellslocated in different levels of the apparatus; a module to activate asignal associated with the access line and cause the signal to remainactivated during a memory operation of obtaining information stored inthe first and second memory cell strings:, a sense amplifier to sensethe data line during a first time interval of the memory operation andprovide first sensed information based on a value of information storedin a memory cell of the first memory cell string and to sense the dataline during a second time interval of the memory operation and providesecond sensed information based on a value of information stored in amemory cell of the second memory cell string; and a latch coupled to thesense amplifier to latch the first sensed information and the secondsensed information, wherein the module is configured to set the latchduring a time interval between the first and second intervals.
 11. Anapparatus comprising: an access line; a data line; a first memory cellstring coupled to the access line and the data line, the first memorycell string including memory cells located in different levels of theapparatus; a second memory cell string coupled to the access line andthe data line, the second memory cell string including memory cellslocated in different levels of the apparatus; a module to activate asignal associated with the access line and cause the signal to remainactivated during a memory operation of obtaining information stored inthe first and second memory cell strings; a sense amplifier to sense thedata line during a first time interval of the memory operation andprovide first sensed information based on a value of information storedin a memory cell of the first memory cell string and to sense the dataline during a second time interval of the memory operation and providesecond sensed information based on a value of information stored in amemory cell of the second memory cell string; a node configured toreceive voltage greater than ground potential during the first andsecond time intervals; and a transistor coupled between the node and thedata line, the transistor configured to turn on during the first andsecond time intervals, and to turn off during a time interval betweenthe first and second time intervals.